(A) The iron-loaded IscA (100 μM) was incubated with Tris (20 mM; pH 8.0), NaCl (200 mM), dithiothreitol (2 mM) and 1 mM each of 2-mercaptoethanol (BME), N-acetyl-L-cysteine (NAC), glutathione (GSH), L-cysteine (L-Cys) and D-cysteine (D-Cys) respectively at 37 °C for 20 min. The samples were then desalted using a HiTrap desalting column and subjected to UV–visible absorption measurements. (B) The EPR spectra of the same samples as prepared for (A) except that the proteins concentration was approx. 400 μM.